Various types of equipment and systems for assisting in navigation and determining the location of a vehicle such as a boat, truck, automobile or airplane are known to the art. Such equipment and systems include various sensors for magnetic-effect sensing. Examples of common magnetic-effect sensors include Hall effect and magneto-resistive (MR) technologies. Such magnetic sensors can generally respond to a change in the magnetic field as influenced by the presence or absence of a ferromagnetic target object of a designed shape passing by the sensory field of the magnetic-effect sensor. The sensor can then provide an electrical output, which can be further modified as necessary by electronics to yield sensing and control information. The electronics may be located either onboard or outboard of the sensor package.
Various types of non-contact devices are presently available for measuring distance and detecting the linear or rotational position of an object. A magnetic compass is a navigational instrument for finding directions on the earth. A magnetic compass includes a magnetized pointer free to align itself accurately with earth's magnetic field, which is of great assistance in navigation. The face of the compass generally highlights the cardinal points of north, south, east and west. Magnetic position sensors utilized by the magnetic compass measure the direction and magnitude of magnetic fields by employing the MR effect. Such sensors include two galvanic separated Wheatstone bridges for sensing the position of a magnetic object. Such magnetic position sensors are generally non-contact sensors. As the magnetized pointer approaches the sensing device, the magnetic field of the pointer is detected and the sensing device generates an electrical signal that is then used for counting, display purposes, recording and/or control purposes.
Navigation generally requires a magnetic compass having an angular resolution of 0.01 to 0.001 degree or better for precise position determination, especially in a Global Positioning System (GPS) denied environment. Similarly, relative versus absolute azimuth resolution of the magnetic compass must also be high. Conventional magnetic position sensors provide a precision of about 0.1 degree, are expensive, and are limited to an accuracy of about 5.5 millidegrees (i.e., 16 bits).